1. Field of the Invention
The present invention relates to a BPSK demodulator, particularly to a low power consumption BPSK demodulator.
2. Description of the Prior Art
The conventional coherent binary phase shift keying (BPSK) demodulators can be classified into the Squaring loop and the Costas loop. The Squaring loop retrieves the carrier frequency signal with a squaring operation and doubles the carrier frequency. Thus, the Squaring loop needs a phase-locked loop (PLL) to lock the signal at the doubled carrier frequency. The phase-locked loop locking the doubled carrier frequency consumes more power. The Costas loop includes two parallel phase-locked loops, which are respectively the I branch and the Q branch with a 90-degree phase difference therebetween. In a general approach, an oscillator generates a signal with a doubled carrier frequency; then an orthogonal signal generator generates two signals having the same frequency and a 90-degree phase difference therebetween. The oscillator is locked at the doubled carrier frequency, consuming more power also. Therefore, the conventional coherent BPSK demodulators have the features: 1. high power consumption, whose reason has been mentioned above; 2. limited data rate, which is because the data rate is limited by the setting time of the phase-locked loop; 3. complicated circuits, which are because the phase-locked loop is a more complicated feedback system; 4. large layout area, which is because the loop filter occupies much area and is unfavorable for biomedicine application.
The devices, which stringently demand low power consumption and low heat radiation, such as implanted biomedicine chips, environment monitoring systems, and Internet of Things (IoT), need a low-power consumption and small-area demodulator to receive data. The conventional demodulators are hard to satisfy the abovementioned requirements because they consume too high a proportion of power used by the overall system.
Thus, the manufacturers in the field are making much effort to develop a low power consumption BPSK demodulator.